1.从Object到String
 要先用Object对象构造一个JSONObject或者JSONArray对象，然后调用它的toString()方法即可

（1）示例一

1 Book book=new Book();
2 book.setName("Java");
3 book.setPrice(52.3f);
4 JSONObject object=JSONObject.fromObject(book);
5 System.out.println(object.toString());

（2）示例二

 1         Book book=new Book();
 2         book.setName("Java");
 3         book.setPrice(52.3f);
 4         
 5         Book book2=new Book();
 6         book2.setName("C");
 7         book2.setPrice(42.3f);
 8         List list=new ArrayList();
 9         list.add(book);
10         list.add(book2);
11         JSONArray arry=JSONArray.fromObject(list);
12         System.out.println(arry.toString());
13 //结果如下：
14 [{"name":"Java","price":52.3},{"name":"C","price":42.3}]

2.从String到Object
 要先用String对象构造一个JSONObject或者JSONArray对象
(1)示例一 

1 String json="{name:'Java',price:52.3}";    
2 JSONObject object=JSONObject.fromObject(json);
3 System.out.println(object.get("name")+" "+object.get("price"));

(2)示例二

1 String json="[{name:'Java',price:52.3},{name:'C',price:42.3}]";
2 JSONArray array=JSONArray.fromObject(json);
3 for(int i=0;i
4     Map o=(Map)array.get(i);
5     System.out.println(o.get("name")+" "+o.get("price"));
6 }

3.从String到Bean

(1)单个Bean对象

1         String json="{name:'Java',price:52.3}";
2         JSONObject object=JSONObject.fromObject(json);
3         Product product=(Product)JSONObject.toBean(object,Product.class);
4         System.out.println(product.getName()+" "+product.getPrice());

(2).Bean的数组

1         String json="[{name:'Java',price:52.3},{name:'C',price:42.3}]";
2         JSONArray array=JSONArray.fromObject(json);
3         Product[] products=(Product[]) JSONArray.toArray(array,Product.class);
4         for(Product p:products){
5             System.out.println(p.getName()+" "+p.getPrice());
6         }

自定义封装JSON操作的类

 1 package com.util;
 2 
 3 import java.util.List;
 4 import java.util.Map;
 5 
 6 import net.sf.json.JSONArray;
 7 import net.sf.json.JSONObject;
 8 
 9 public class JsonHelper {
10     //从普通的Bean转换为字符串
11     public static String getJson(Object o){
12         JSONObject jo=JSONObject.fromObject(o);
13         return jo.toString();
14     }
15     //从Java的列表转换为字符串
16     public static String getJson(List list){
17         JSONArray ja=JSONArray.fromObject(list);
18         return ja.toString();
19     }
20     //从Java对象数组转换为字符串
21     public static String getJson(Object[] arry){
22         JSONArray ja=JSONArray.fromObject(arry);
23         return ja.toString();
24     }
25     //从json格式的字符串转换为Map对象
26     public static Map getObject(String s){
27         return     JSONObject.fromObject(s);
28     }
29     //从json格式的字符串转换为List数组
30     public static List getArray(String s){
31         return JSONArray.fromObject(s);
32     }
33     //从json格式的字符串转换为某个Bean
34     public static Object getObject(String s,Class cls){
35         JSONObject jo=JSONObject.fromObject(s);
36         return JSONObject.toBean(jo, cls);
37     }
38     //从json格式的字符串转换为某类对象的数组
39     public static Object getArray(String s,Class cls){
40         JSONArray ja=JSONArray.fromObject(s);
41         return JSONArray.toArray(ja, cls);
42     }
43 }